Background: Multimorbid Veterans-patients with multiple, often interacting, health conditions-face complex self-care challenges and account for a disproportionate share of the VA's health care utilization and costs. eHealth applications-patient-facing technology such as personal health records, web-based disease management programs, and secure patient-provider communication tools-offer an opportunity to support patients' self-care, enhance communication with caregivers and providers, and encourage appropriate health care utilization. The VA has developed a number of eHealth tools and is devoting substantial resources to their growth and implementation. There is a need, however, to determine how this technology can be optimized to help Veterans and caregivers manage challenges specific to multimorbidity. Objectives: This research aims to optimize eHealth technology for Veterans with multiple chronic conditions by: 1) Describing how multimorbid patients and their caregivers use eHealth technology and how their needs might be better met, 2) Determining the impact of multimorbid patients' eHealth use on their health behaviors, utilization, and health care costs, and 3) Developing eHealth interventions that support multimorbid Veterans' self-care and encourage appropriate and cost-effective utilization of care. Methods: We propose to use a sequential mixed-methods approach based on implementation science principles to inform the development of eHealth interventions for multimorbid Veterans and their caregivers. The first study will evaluate the current and potential role of eHealth technology in supporting the health and health care needs of multimorbid Veterans (Aim 1). This study will use focus groups (Aim 1.1) to explore how eHealth technology helps patients and caregivers overcome challenges associated with multimorbidity, to identify barriers and facilitators to their use of eHealth technology, and to determine their preferences for technological tools. Focus group findings will be complemented by usability testing (Aim 1.2) of the VA's personal health record-My HealtheVet-among multimorbid Veterans. These early qualitative evaluations will inform a subsequent national survey that examines the clinical and financial impact of eHealth use by multimorbid Veterans following hospitalization (Aim 2). The population for this study will comprise multimorbid Veterans with heart failure-a condition for which there is substantial evidence detailing the negative consequences of comorbidities-and will focus on the period following hospitalization when there are heightened self-care challenges and high utilization rates. The survey will query patients (or their caregivers) about eHealth technology use, and responses will be linked to clinical and administrative data over the following year to explore th value of eHealth, and its association with outcomes of interest (e.g., medication adherence, urgent care visits, health care costs). Ultimately, the results from formative qualitative (Aim 1) and quantitative (Aim 2) studies will inform the development of a pilot eHealth intervention to support multimorbid heart failure patients who are transitioning from hospital to home (Aim 3). This study will employ a user-centered design process that incorporates feedback from patients and caregivers, as well as clinical and operational partners, to evaluate feasibility and implementation. Career Development: Research activities will be supplemented by close interactions with operational partners, as well as training activities in three domains that draw on mentors' expertise and are critical to the PI's long-term research and career goals: 1) Implementation science (Mentor: Steven M. Asch), 2) Clinical and consumer health informatics (Mentors: Mary K. Goldstein, Thomas K. Houston), and 3) Health economics (Mentor: Todd H. Wagner). These research and training activities will facilitate the PI's growth as an independently-funded health services researcher with expertise to develop, evaluate, and implement novel technology that improves the health and health care of multimorbid Veterans.